The present invention relates to refrigeration units in general and, more in particular, to an apparatus and method for determining whether a refrigeration unit is operating efficiently.
Obviously refrigeration units consume power. The efficiency of a refrigeration unit measures the amount of refrigeration effected for the power consumed in effecting the refrigeration. Clearly, the higher a refrigeration unit efficiency, the better its performance.
A refrigeration cycle takes cold refrigerant in liquid form and passes that refrigerant in heat exchange relationship with a cooling load in an evaporator. The refrigerant takes on heat and in so doing cools the load. The refrigerant is largely vaporized in the evaporator and leaves it in that state. As a vapor, the refrigerant is isentropically compressed to raise its pressure for introduction into a condenser. In the condenser the refrigerant is in two phases, liquid and vapor. A coolant, say cooling water, effects condensation of the refrigerant in the condenser by passing in heat exchange relationship with the refrigerant. There is a phase change, then, in the condenser. Refrigerant from the condenser expands adiabatically to reduce its temperature and passes again in heat exchange with load in the evaporator.
This idealized cycle forms the basis for an optimum efficiency determination. Performance falls short of this standard for several reasons. One such reason is that there are non-condensibles in the refrigerant. Another reason is fouling of the condenser. Other reasons include the condenser being overcharged with too much refrigerant and improper cooling water flow. This causes results in excessive pressure in the condenser head space. Inadequate cooling water flow through the condenser also results in a condenser head space pressure which is too high for the actual load, but which is too low relative to optimum, based on observance of only coolant temperature difference across the condenser.
These known causes of less than optimum efficiency have not been easily determined on a continuous basis and as a result too many refrigeration units operate inefficiently. With inefficient operation, too much energy is consumed.